There is no cure for herpes simplex virus (HSV) latent infections of neurons, and the possibility of asymptomatic reactivation and simultaneous transfer of infectious virus via mucous membranes is a significant drawback of current therapies. We have pioneered the study of selective inhibitors of the herpes virus-specific thymidine kinase (TK), the enzyme responsible both for activation of anti-herpes nucleoside analogs and for reactivation of virus from the latent state in sensory nerve ganglia. Animal studies, however, have required intraperitoneal dosing of test compounds because the compounds are poorly soluble in water and not sufficiently orally available to warrant study of their effectiveness by the oral route. Among strategies to enhance oral absorption of candidate drugs, we have synthesized the 6-deoxy analogs of two promising compounds, and have found that one of these, which we call SacrovirTM, has moderate oral absorption in the mouse, which is enhanced by mixing with the solubilizing polymer Soluplus, and is converted nearly completely into the ultimate drug N2-[m-(trifluoromethyl) phenyl] guanine, mCF3PG. Thus, we propose to develop one or more formulations that will greatly increase the oral absorption of Sacrovir and show oral efficacy in animal models of HSV reactivation. To achieve this goal, our specific aims are to: 1. formulate the pro-drug Sacrovir (6-deoxy-mCF3PG) to enhance its intestinal absorption; strategies include emulsions, small molecule adjuvants, and solubility enhancers; 2. Compare oral bioavailability of Sacrovir formulations in the mouse, by analyzing plasma samples by LC-MS methods for both the pro-drug and the ultimate drug mCF3PG; 3. determine the oral bioavailability of mCF3PG in rabbits and guinea pigs after oral treatment with Sacrovir; and 4) test, through collaborators, the efficacy of oral Sacrovir in rabbit and guinea pi models of HSV reactivation. Following successful demonstration of an optimal oral formulation of Sacrovir, the experiments of aim 4 to test efficacy in rabbit and guinea pig models, respectively, will be conducted by subcontractor Dr. James M. Hill at LSU Health Sciences Center, New Orleans, and by Drs. David Bernstein and Rhonda Cardin of Cincinnati Children's Hospital Medical Center, under contract from NIAID (Dr. Heather Greenstone, Antiviral Branch). Positive results will be used as background to secure additional funding, for example through a phase II small business grant, and ultimately from a corporate sponsor or licensee, to fully develop the drug. The pro-drug Sacrovir will represent a first-in-class, novel oral treatment for HSV latent infections of neurons and, importantly, will prevent both asymptomatic virus shedding and the resulting transmission of infection to sex partners. PUBLIC HEALTH RELEVANCE: There is no cure for herpes simplex virus infections; asymptomatic reactivation of virus from the latent state in neurons and its transfer via mucous membranes is a significant drawback of current therapies. We have synthesized a pro-drug SacrovirTM that is both orally absorbed in mice and converted metabolically to the ultimate anti-reactivation drug, mCF3PG. In this project we will develop a formulation of Sacrovir that will increase its oral absorption in mice, and show that this formulation will have efficacy in rabit and guinea pigs models of herpes simplex reactivation. Sacrovir represents a first-in-class, novel oral treatment for latent herpes simplex infections of neurons and, importantly, will prevent transmission of infectious virus.